In the prior art, it is known, for example, that athletes perform respiratory training under a reduced oxygen partial pressure that simulates training at a higher elevation as so-called altitude training in order to increase athletic performance at lower elevations. Positive effects are based substantially on the body's adaptive response under hypoxic conditions, so that such training performed under a reduced O2 partial pressure can have a physically as well as mentally positive influence on performance.
The simulation of respiration at high altitude is here basically achieved by setting a reduced O2 partial pressure in the respiratory gas intended to be inhaled, as compared to such pressure at conventional elevations such as, for example, at sea level.
Instead of actually training at the corresponding altitude, the desired outcome can be achieved with an apparatus of the above-described kind, with which a person who is training exhales respiratory gas into a closed space and inhales it from this closed space, so that the inhaled inspiration gas is composed at least in part of the exhaled respiratory gas and the O2 partial pressure is therefore lowered by the oxygen consumption of the person breathing. The prior art therefore includes a kind of pendulum breathing, during which the person breathing always inhales back a part of the exhaled respiratory gas (expiration gas).
Here, one speaks of respiratory gas instead of breathing air because the term “air” suggests a fixed, specific gas composition, but this in fact changes with the apparatus relative to the composition of normal air, especially with respect to the partial pressures of oxygen and carbon dioxide.
For this purpose, the apparatus known in the prior art has a closed space that is formed at least in part by a variable-volume container provided on a mouthpiece, for example, a mouthpiece that is to be taken into the mouth or even a mask that is to be worn. Selecting the size of the container volume makes it possible to influence the total closed space of such an apparatus, and thus to also influence the proportion of the exhaled respiratory gas (expiration gas) that is inhaled back by the person who is training. Selecting the container volume therefore makes it possible, with the apparatus of the prior art, to adjust the O2 partial pressure at which the person training performs the respiratory training, e.g., altitude training.
The respiratory training made possible thereby or a method of performing the method, in particular with the above-described apparatus, preferably entails such a method as is not performed by a person for therapeutic purposes, but rather preferably only for the purpose of enhancing athletic performance.
The apparatus or method previously known in the prior art for performing such respiratory training, for example altitude training has a disadvantage in that, although the oxygen partial pressure can be influenced by altering the container volume or the total closed space of a corresponding apparatus (in particular, the oxygen partial pressure can be reduced by increasing the closed space), the result of so doing, in connection with this change of the oxygen partial pressure, is that the CO2 partial pressure in the respiratory gas within the above-described closed space and thus in the respiratory gas that is to be inhaled (inspiration gas) is influenced simultaneously as well, and in particular such that, with the increase of the container volume and thus the decrease of the O2 partial pressure, an increase of the CO2 partial pressure is set, which has adverse effects on the body of the person training.
An apparatus has therefore also become known by which the process of inhalation takes place through a filter that is filled with an absorber material in order to absorb CO2 from the inhaled air. However, this is problematic in that fine dust in the absorber could potentially reach the lungs of the person training, with potentially negative effects or even as a result of a considerable breathing resistance produced by the filters intended to be used, especially those that prevent the entry of particulate matter.
The absorption of the exhaled CO2 is a time-dependent quantity, such that the CO2 partial pressure (CO2 concentration) in the respiratory gas (inspiration gas) is also time-dependent. Once the absorption efficiency is no longer 100%, then the CO2 concentration in the respiratory gas (inspiration gas) rises in an undefined manner.
There are also specific uses in which, in addition to adjusting a specific O2 partial pressure, it is desired to also adjust a specific CO2 partial pressure that cannot be achieved with the conventional apparatus of the prior art, for lack of an explicit controllability, especially of the CO2 partial pressure.